1. Field of the Invention
The present invention relates to a process for producing an indoline derivative having high purity in high yield.
2. Description of the Prior Arts
Indoline derivatives are important compounds as intermediates for indoles used as starting materials for agricultural chemicals, medicines, perfumes and dyes. Various processes have been proposed as the process for producing indoline derivatives;
(1) A cyclization of 2-Aminophenethyl alcohol is carried out in the presence of hydrochloric acid (Kagaku Daijiten Vol. 4 page 409 Kyoritsu K.K.) and;
(2) Stannous chloride and conc. hydrochloric acid are added to 2-nitrophenethyl bromide to obtain 2-aminophenethyl bromide and a cyclization of 2-aminophenethyl bromide is carried out to obtain the indolines (J. of the American Chemical Society Vol. 63, page 1563 (1941)).
However, the cyclization of 2-aminophenethyl alcohol in the presence of hydrochloric acid has disadvantages that 2-aminophenethyl alochol is thermally unstable to be easily polymerized to produce a by-product of the polymer. It is difficult to obtain indolines having high purity in high yield.
On the other hand, the process of using 2-nitrophenethyl bromide has a disadvantage of low yield of the object indolines.
The inventors have studied to overcome these conventional disadvantages and have proposed a cyclization of 2-halogenophenethylamines in the presence of a copper catalyst and ammonia (Japanese Unexamined Patent Publication No. 98961/1978). However, in this process, ammonia in a form of gas, liquid or solution is used, and accordingly, it is necessary to carry out the reaction in an autoclave under a pressure of 5 to 35 kg/cm.sup.2. Thus, an autoclave is required as a reactor and the reactor should be anticorrosive in view of a by-product as an aqueous solution of ammonium halide. Moreover, the treatment of the wasted water containing ammonium halide is serious problem.